System for controlling three-dimensional coordinate transformation

ABSTRACT

A three-dimensional coordinate transformation control system controls three-dimensional coordinate transformation in a computerized numerical control apparatus for controlling a machine tool having a plurality of heads. A pre-processing calculating unit (2) decodes a machining program (1), effects three-dimensional coordinate transformation for only a first head in a three-dimensional coordinate transforming unit (3), and distributes pulses based on transformed coordinates to a pulse distributing unit (4). For a second head, the coordinates for the first head are used as they are, and pulses based on the coordinates are distributed by a pulse distributing unit (5). The three-dimensional coordinate transformation is therefore calculated by a reduced number of times, and the burden on the computerized numerical control apparatus for calculations is reduced.

BACKGROUND OF THE INVENTION

The present invention relates to a system for controllingthree-dimensional coordinate transformation in a computerized numericalcontrol apparatus for controlling a machine tool having a plurality ofheads, and more particularly to a three-dimensional coordinatetransformation control system which is capable of simply calculatingthree-dimensional coordinate transformation.

DESCRIPTION OF THE RELATED ART

Machine tools with a plurality of heads are used to machine a pluralityof identical workpieces simultaneously. These heads areparallel-controlled by a computerized numerical control apparatus. Whilethe machine tools with plural heads are generally controlled accordingto a single machining program, the heads are controlled by respectiveinternal calculations, e.g., preprocessing calculations.

When three-dimensional coordinate transformation is to be executed withrespect to conventional parallel axes, it has been customary todetermine transformation formulas for the respective heads and effectcalculations according to the determined transformation formulas eventhough the same motion command is given. Stated otherwise, as manycoordinate transformation calculations as the number of heads used havebeen carried out.

Since the three-dimensional coordinate transformation is calculatedusing a transformation matrix, however, the amount of calculationsneeded is considerable, placing a large burden on the processing time ofthe computerized numerical control apparatus.

With the parallel-axis control, if the same motion command is given,then coordinates that have been transformed into the three-dimensionalcoordinate system are common for the heads. Therefore, thethree-dimensional coordinate transformation may be calculated withrespect to only one of the heads, and the calculated coordinates for thehead may be employed with respect to the other heads without calculatingthe three-dimensional coordinate transformation for those other heads.

SUMMARY OF THE INVENTION

In view of the above drawbacks of the conventional three-dimensionalcoordinate transformation control system, it is an object of the presentinvention to provide a three-dimensional coordinate transformationcontrol system which is capable of simply calculating three-dimensionalcoordinate transformation.

In order to achieve the above object, there is provided in accordancewith the present invention a system for controlling three-dimensionalcoordinate transformation in a computerized numerical control apparatusfor controlling a machine tool having a plurality of heads, comprisingpre-processing calculating means for decoding a machining program,effecting three-dimensional coordinate transformation for a first head,and outputting pulse distribution data, and a plurality of pulsedistributing means associated respectively with the heads of the machinetool, for distributing pulses In response to the pulse distribution datafrom the preprocessing calculating means.

The preprocessing calculating means executes three-dimensionalcoordinate transformation for only a first head. For the other head orheads, the transformed coordinates are used as they are, and pulses aredistributed on the basis of the transformed coordinates. In this manner,the three-dimensional coordinate transformation is calculated by areduced number of times, and the burden on the computerized numericalcontrol apparatus for calculations is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a three-dimensional coordinatetransformation control system according to an embodiment of the presentinvention; and

FIG. 2 is a block diagram of a hardware arrangement of a computerizednumerical control (CNC) apparatus for implementing the principles of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will hereinafter be describedwith reference to the drawings.

FIG. 1 shows in block form a three-dimensional transformation controlsystem according to an embodiment of the present invention. In theillustrated embodiment, the three-dimensional transformation controlsystem will be described for the control of a machine tool having twoheads. A pre-processing calculating unit 2 provides means for reading amachining program 1, decodes the machining program 1, and calculatespulse distribution data. For example, the pre-processing calculatingmeans 2 determines which plane a given command belongs to, whetherinterpolation is linear or circular, etc., and produces necessary pulsedistribution data.

The pre-processing calculating means 2 includes a three-dimensionalcoordinate transforming unit 3. The three-dimensional coordinatetransforming unit 3 is required, for example, when a head is controlledto be perpendicular to a slanted surface for drilling the slantedsurface. In this case, the three-dimensional coordinate transformingunit 3 provides means for performing three-dimensional coordinatetransformation from an ordinary coordinate system into a coordinatesystem perpendicular to the slanted surface.

The three-dimensional coordinate transforming means 3 effectsthree-dimensional coordinate transformation on the pulse distributiondata for the first head, and transmits the pulse distribution data to apulse distributing unit 4 and a pulse distributing unit 5. Thethree-dimensional coordinate transformation is therefore carried outonce. The pulse distributing unit 4 provides means for controlling thefirst head, whereas the pulse distributing unit 5 provides means forcontrolling the second head.

The pulse distributing means 4 outputs distributed pulses XPI, YPl, ZPlfor controlling the first head to respective servomotors. The pulsedistributing means 5 outputs distributed pulses XP2, YP2, ZP2 forcontrolling the second head to respective servomotors.

FIG. 2 shows in block form a hardware arrangement of a computerizednumerical control (CNC) apparatus for implementing the principles of thepresent invention. The computerized numerical control (CNC) apparatus,generally denoted by the reference numeral 10, has a processor 11 forcontrolling overall operation of the computerized numerical control(CNC) apparatus. More specifically, the processor 11 reads a systemprogram stored in a ROM 12, and controls overall operation of thecomputerized numerical control (CNC) apparatus according to the readsystem program. A RAM 13 temporarily stores calculated data, displaydata, and other data, the RAM 13 comprising an SRAM. A CMOS 14 storestool correctives, pitch error correctives, a machining program, andparameters. Although not shown, the CMOS 14 is backed up by a battery sothat it serves as a nonvolatile memory even when the power supply of thecomputerized numerical control (CNC) apparatus 10 is turned off.Therefore, the data stored in the CMOS 14 are stored even when thecomputerized numerical control (CNC) apparatus 10 is de-energized.

An interface 15 serves to connect an external device 31 to thecomputerized numerical control (CNC) apparatus 10, the external device31 comprising a paper tape reader, a paper tape puncher, a paper tapereader/puncher, or the like. A NC program is read from the paper tapereader, and the machining program edited in the computerized numericalcontrol (CNC) apparatus 10 may be output to the paper tape puncher.

A PMC (programmable machine controller) 16 controls the machine toolaccording to a sequence program of ladder configuration which is storedin the CNC 10. Specifically, the PMC 16 converts M, S, and T functionsspecified according to the machine program into signals required by themachine tool according to the sequence program, and outputs the signalsthrough an I/O unit 17 to the machine tool. The output signals energizeelectromagnets in the machine tool, thereby activating hydraulic valves,pneumatic valves, and electric actuators. The PMC 16 also receivessignals from limit switches in the machine tool and switches on amachine control console, processes the received signals as required, andtransfers the processed signals to the processor 11.

A graphic control circuit 18 converts digital datas, i.e., presentpositions of the axes, alarms, parameters, and image data into imagesignals, and outputs the image signals. The image signals are sent to adisplay device 26 in a CRT/MDI unit 25, and displayed on the displaydevice 26. An interface 19 receives data from a keyboard 27 in theCRT/MDI unit 25, and transfers the received data to the processor 11.

An interface 20 is connected to a manual pulse generator 32 and receivespulses from the manual pulse generator 32. The manual pulse generator 32is mounted on the machine control console, and is manually operated toposition movable components of the machine tool with precision.

Axis control circuits 41 through 44 receive motion commands for the axesfrom the processor 11, and outputs the received motion commands toservoamplifiers 51 through 54, respectively. In response to the motioncommands, the servoamplifiers 51 through 54 energize respectiveservomotors 61 through 64 for the respective axes. The servomotors 61through 64 have built-in pulse coders as angular position detectors forproducing position signals that are fed back as pulse trains. Linearscales may be employed as the position detectors. The pulse trains maybe converted from frequency to velocity (F/V) so that velocity signalscan be generated from the pulse trains. The feedback lines for theposition signals and the feedback of the velocity signals are omittedfrom illustration. The servomotors 61, 62 serve to control the firsthead, whereas the servomotors 63, 64 serve to control the second head.Axis control circuits, servoamplifiers, and servomotors for Z1 and Z2axes are omitted from illustration.

Spindle control circuits 71, 72 output spindle speed signals torespective spindle amplifiers 81, 82 in response to spindle rotationcommands and commands for the orientation of spindles. Responsive to thespindle speed signal, the spindle amplifiers 81, 82 energize therespective spindle motors 91, 92 to rotate at commanded rotationalspeeds.

With the present invention, as described above, three-dimensionalcoordinate transformation is carried out in order to control the firsthead, thereby determining pulse distribution data. The determined pulsedistribution data are output to the pulse distribution means forcontrolling the other head. Therefore, the three-dimensional coordinatetransformation is carried out only once, thereby lessening the burden onthe computerized numerical control apparatus for calculations andshortening the time required for the calculations.

What is claimed is:
 1. A system for controlling three-dimensional coordinate transformation in a computerized numerical control apparatus for controlling a machine tool having a plurality of heads, comprising:pre-processing calculating means for decoding a machining program, effecting three-dimensional coordinate transformation for a first head, and outputting pulse distribution data; and a plurality of pulse distributing means associated respectively with the heads of the machine tool, for simultaneously distributing pulses to the plurality of heads in response to the pulse distribution data from said pre-processing calculating means for the first head. 